Various types of damper devices have been developed over the years to control the flow of fluid through ducts in low velocity HVAC systems (i.e., provide zone control). The damper devices are used to control the flow of air through the systems' air ducts and range from a simple hand-tumable damper vane often found in residential buildings to motor driven mechanical damper assemblies more commonly used in commercial and industrial structures. Another type of damper device employs an inflatable bladder or bellows to control fluid flow through a duct, and details of particularly useful bladder-type flow control devices and associated systems can be found in U.S. Pat. Nos. 4,545,524, and 4,702,412. One advantage of the bladder-type flow control devices shown in these patents is that they could be easily retrofitted into existing ducts with minimal difficulty.
Another prior art type of damper device for low velocity HVAC systems is a mechanical damper assembly comprising a short piece of metal duct in which a damper vane is provided with a shaft that is pivotally mounted for rotation in the short piece of metal duct. The damper vane is rotated between open and closed positions by a motor mounted to and outside the duct piece and connected to the damper vane shaft.
The aforesaid type of mechanical damper assembly is somewhat difficult to install in an existing low velocity metal duct. Installation requires the duct piece of the damper assembly to be spliced into the existing low velocity duct. This involves cutting out a length of the existing metal duct and usually dismantling of the existing metal duct to enable such cutting and/or assembly of the duct piece between adjacent sections of the existing duct. This dismantling, cutting, and reassembling of the metal ductwork is time consuming and, therefore, an expensive operation when performed by paid installers.
The damper vanes in prior art mechanical damper assemblies heretofore have been driven by both electric and fluid motors. A drawback of electric damper motors is that often their life cycle is comparatively short and limited, thereby making motor replacement a relatively frequent and expensive maintenance operation. Another problem is that, in systems employing a considerable number of electric motor driven dampers, relatively complicated wiring schemes and transformers are often involved, all adding to the cost and complexity of the overall system. Fluid motors eliminate the electrical wiring problems and often have comparatively longer life cycles, but they too have had drawbacks associated therewith. Even with so-called frictionless diaphragm-type fluid motors, the actuator members thereof are typically engaged by bearings and wipers that still hinder free linear movement of the members. Also, to reduce friction, the members are often made of hardened steel as opposed to less expensive materials.
U.S. Pat. No. 5,458,148, which is incorporated herein by reference, describes a fluid flow control damper assembly that overcomes many of the drawbacks associated with the damper assemblies described above herein. In this patent, a damper assembly comprises a support base for external mounting to a side of a duct. A damper vane is mounted to the support base for movement between open and closed positions. The damper vane is located inwardly of the inner side of the support base for positioning interiorly of the duct when the support base is mounted to the duct. An actuator is mounted to the support base and operatively connected to the damper vane for moving the damper between open and closed positions. The support base includes a closure for closing an access opening in a side wall of the duct of sufficient size to permit insertion of the damper vane therethrough. The closure includes a mounting member and a gasket at the inner side of the mounting member for providing a seal between the mounting member and the side wall of the duct. The actuator includes a fluid motor of the type including a diaphragm. The damper vane may be pivotally mounted to the end of a mounting post extending inwardly from the support base and the fluid motor may have an actuator member connected to the diaphragm and extending generally parallel to the mounting post for connection to the damper vane.
For SDHV HVAC systems, zone control has been difficult and largely impractical due to a lack of sufficient damper assemblies designed for the unique properties and characteristics of SDHV HVAC systems (e.g., higher air velocities and pressures than that of traditional low velocity HVAC systems and smaller diameter duct work, for example, 2 inch diameter duct work). Therefore, a need exists for a damper assembly that may be used in SDHV HVAC systems.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such systems and methods with the present invention as set forth in the remainder of the present application with reference to the drawings.